Prince Harry is said to be "very sad" about the distance between his two children and the Royal Family.To celebrate Archie's seventh birthday on Wednesday, Meghan Markle released a heartwarming unseen photo of the young prince resting on Harry's chest.Archie appeared to be merely days old, which suggests the image is likely to have been captured in Frogmore Cottage, Windsor, where the Sussexes previously resided.But the photo is merely a snapsho…